In a wireless communications system, such as a code division multiple access (CDMA) system, signals suffering from a high peak-to-average ratio (PAR) can cause inefficiencies in the digital-to-analog (D/A) conversion and in the power amplifier (PA) stages of transmission. In many cases, signals may be clipped beyond a preset threshold so that high PAR signal envelopes are bounded and D/A converter bit-widths are kept in check. In some cases further filtering may be performed on clipped signals before transmission, adding to the complexity of the communications system.
In general, clipping achieves higher PA efficiency at the expense of spurious out-of-band emissions. That is, extra spurious signal energy is emitted out of the bandwidth originally assigned to the signal. This will have adverse effects in most communications systems as the spurious signal energy has gone out of an intended band into neighboring bands. There is also a limit as to how much of the signal can be clipped. Namely, clipping the signal more results in higher PA efficiency at the expense of more out-of-band emissions. Moreover, while clipping may limit a signal to preferred levels, the signal is permanently deteriorated.